Cape Town - Mercedes and Ferrari have both brought upgraded engines to the Belgian Grand Prix weekend, with Valtteri Bottas and Kimi Raikkonen braced for grid penalties. 

Lewis Hamilton and Sebastian Vettel confirmed on Thursday that their respective teams are ready to roll out their Spec-3 engines at Spa taking them both to their limit for the season before penalties are incurred for changing power unit elements. 

Bottas and Raikkonen, though, are already on the limit with some elements and are set to move toward the back of the grid as a result once the FIA has received confirmation from both teams about the specific elements they are going to introduce. 

"Naturally every upgrade that we have and every opportunity there is for an upgrade is important," said Hamilton. 

"These are two big power circuits we've got these next two weekends. This weekend I think they've got a new power unit, we will have a new power unit. 

"So, it will be interesting to see how they fare with each other, but naturally I've got a lot of confidence." 

Raikkonen is set to feel the biggest benefit of all four of the leading drivers as he has been racing with a Spec-1 engine all season. 

His power unit failed in Spain, which in turn put him out of sync on Ferrari's engine programme. He had to change to a newer version of the old specification and he has used that for the last seven race weekends. 

Elsewhere, Renault's Nico Hulkenberg is also set to rack up engine penalties with a whole new power unit ready to be fitted.